For many applications, it is useful to associate data (metadata) with media signals. Some examples include associating the owner of an image with the image, or associating a picture with a song. One problem is maintaining the association between various types of processing on the media signal or its metadata.
The following disclosure describes several methods, devices and applications for processing metadata, including but not limited to, technology to embed metadata in a media signal, and technology to process metadata that will be or has been embedded in the media signal.
The invention provides methods of processing metadata of media signals such as audio, video and still image signals. These methods persistently associate metadata for a media signal by steganographically embedding metadata into the media signal. Steganograhic embedding inserts the metadata into the content of the signal itself by subtly altering the media signal such that the alterations are imperceptible or substantially imperceptible to the viewer or listener when the signal is rendered. A specific form of steganographic embedding is digital watermarking.
The invention provides various methods for processing the steganographically embedded metadata. For example, images and video are embedded with metadata in the form or compressed voice data. Also, a metadata digest, including descriptors of metadata stored externally, are embedded into the media signal. The metadata digest comprising descriptors of the metadata is extracted and displayed to show the types of metadata associated with a media signal. The user can then select a link to metadata from among the displayed descriptors.
The embedded metadata may be used to authenticate other metadata associated with the media signal in which it is embedded. One aspect of the invention is a method for embedding a metadata signature, such as a hash of external metadata stored outside the media signal, into the media signal itself. The external metadata is located outside the content, such as in a file header or remote database. The external metadata is authenticated by computing a hash, and comparing this hash with the hash of the metadata extracted from the data embedded in the media signal.
The embedded metadata may also include time and location stamps to mark the media signal with a time and location when certain processing events occur. These processing events include editing the media signal or transferring the media signal from one device to another.
Further features will become apparent with reference to the following detailed description and accompanying drawings.